Means for securing turbine-rotors to their shafts



F. LJUNGSTRO'M.

MEANS FOR SECURING TURBINE ROTORS TO THEIR SHAFTS.

APPLICATION FILED APR. I5, 1919. 1,347,344.

Patented July 20, 1920 E m J 7 6' a:

T i E 9 Inventor b FT-edr-ikL junsstr-im,

H is Attorney UNITED STATES PATENT OFFICE.

FREDRIK LJUNGsTRoM, or BREVIK, LIDINGGN, SWEDEN, nssrenon r0 .AKTIE- BOLAGET LJ'UNGSTROMS ANGTURBIN, or STOCKHOLM, SWEDEN, A CORPO- RATION.

MEANS FOR SECURING TURBINE-ROTORS TO THEIR SHAFTS.

Specification of Letters Patent.

Patented July 20, 1920.

Application filed April 1 5, 1919. Serial No. 290,355.

To all whom it may concern:

Be it known that I, FREDRiK LJUNGs'rRoM, a subject of the King of Sweden, residing at Brevik, Lidingon, Sweden, have invented certain new and useful Improvements in Means for Securing Turbine-Rotors to Their Shafts, of which the following is a specification.

The present invention relates to means for securing turbine rotors to their shafts and has for its object to provide an improved structure and arrangement for keeping the parts tight at all times.

For a consideration of what I believe to be novel and my invention, attention is directed to the accompanying description and the claims appended thereto.

In the'drawing which illustrates an embodiment of my invention, the figure is an axial, sectional view of a part of a turbine shaft and a rotor carried thereby.

Referring to the drawing, 1 indicates a part of a rotor upon which are mounted concentric rows of blades 2. In the type of turbine to which my invention more especially relates, two rotors are provided arranged face to face with concentric rows of axially extending blades between and through which the steam flows radially outward. The rotor is provided with a hub 3 containing slots 4 through which steam flows from a suitable source to the inner blade ring. The hub 3 is provided with a conical bore to receive one end of a stub shaft 5 and the two parts are held against relative'rotation by a plurality of spaced keys 6 which may be made advantageously of round stock finished to the required size. These keys have a slight taper from their inner to their outer ends so that when moved outwardly from the center of the machinethey will prevent any play from existing in the key slots.

Stub shaft 5 is made hollow and inside of Tubular member 6 is connected at its outer end to stub shaft 5 by a threaded engagement as indicated at 7. At its inner end tubular member 6 is provided with a flange or shoulder 8 which engages hub 3 to hold it on the tapered end of stub shaft 5. By turning the tubular member 6 the threaded engagement 7 will pull flange 8 into engagement with hub 3, thereby firmly pulling the hub on the end of the stub shaft and at the same time put-- ting the member 6 under tension.

By calculation or experiment, or both, it is determined how much the bore of the hub will enlarge due to temperature changes. It is evident that if the hub expands more quickly than the shaft it will become loose. It is further evident since the contacting surfaces of the shaft and the wall of the bore are conical that the parts can again be made tight if, when the hub expands, the shaft and the hub are drawn together. This function is performed by the tension member 6. Having determined what the maximum enlargement of the hub will be and how much axial movement is necessary to bring the parts into firm contact under all conditions, the tension member is so designed that it will, when cool, be stretched by an amount somewhat greater than the total amount of the relative axial movement between the hub and stub shaft at any time. As a result of this, when the hub enlarges for any reason the tension member will force the hub farther onto the shaft with the effect of keeping it tight. To state the matter in another way, the tension member is always seeking to shorten itself and will do so whenever there is the slightest looseness between the hub and theshaft.

The member 6 is made hollow and is provided with an end wall 10 in which is a hole 11 to allow steam to enter the hollow stub shaft 5. A nut 12 is provided for the purpose of preventing steam from passing into the joint between the stub and the main' shafts.

through tension member 6 into the hollow shaft 5 so as to heat it, thereby tending to keep its temperature substantially the same as that of the hub 3. By this arrangement the hub 3 and stub shaft 5 will tend to expand and contract with temperature changes at substantially the same rate. v

The present invention is a modification of and relates to apparatus of the character shown in the earlier application of Birger Ljungstrom, Sr. No. 285,032, filed March 25, 1919, means for securing turbine rotors to their shafts.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Ratent of the United States, is

1. In a turbine, the combination of a rotor, a hollow shaft having a tapered end to which the rotor is keyed, and a hollow tension member having a fixed flange on its inner end which engages said rotor, the outer end of said member being connected to said rotor for putting such member under ten- 2. In a turbine, the combination of a 1'0- tor,a hollow shaft having a tapered end to which the rotor is keyed, and a hollow tension member having a flange on its inner end which engages said rotor, the outer end of said member having threaded engagement with said hollow shaft.

In testimony whereof I aflix my signature 25 in presence of two witnesses.

GRETA PRIEN. 

